In connection with conventional IPM rotors, Japanese Patent Laying-Open No. 2002-034187, for example, discloses a magnet embedded rotor aimed at attaining higher reliability (Patent Document 1). The magnet embedded rotor includes a laminated core having a plurality of holes formed therein, permanent magnets inserted to respective holes, and resin member introduced to each hole. Patent Document 1 further discloses an injection metal mold used for manufacturing the magnet embedded rotor. The injection metal mold includes a lower mold to which the laminated core is inserted, and an upper mold having injection holes for supplying resin to respective holes. One injection hole is provided for one hole.
Japanese Patent Laying-Open No. 09-163649 discloses a permanent magnet embedding type motor in which a crack or chipping of the magnet is prevented when the permanent magnet is inserted to a rotor core, for realizing small size, high output and high reliability (Patent Document 2). According to Patent Document 2, an adhesive sheet impregnated with an adhesive or having an adhesive applied, is arranged in a slit hole to which the permanent magnet is inserted.
Japanese Patent Laying-Open No. 2005-012859 discloses a rotor of a motor aimed at improving thermal conductivity between a permanent magnet and a rotor core (Patent Document 3). According to Patent Document 3, a magnet insertion hole is formed in the rotor core. On a surface of the permanent magnet to be in contact with the magnet insertion hole, a coating layer of an elastic material is formed.
As disclosed in Patent Document 1, it has been known to fill a resin material in a gap between the rotor core and the permanent magnet to hold the permanent magnet, when the permanent magnet is embedded in the rotor core. The resin, however, has low fluidity and, therefore, it is possible that the gap is not fully filled with the resin. In such a case, NV (Noise and Vibration) characteristics of the IPM rotor may possibly be degraded.